1. Field of the Invention
The present invention relates to a boring bit for use with a drill, and more particularly to a boring bit having a well-secured blade.
2. Description of Related Art
With reference to FIGS. 5 and 6, a conventional boring bit comprises a head (40) and a blade assembly (43). The head (40) has a top, an external surface, a mounting recess (41) and two holding protrusions (42). The mounting recess (41) is formed on the external surface of the head (40) near the top and has a bottom and a threaded hole (not numbered). The threaded hole is formed in the bottom of the mounting recess (41). The holding protrusions (42) are formed on and protrude from the bottom of the mounting recess (41) beside the threaded hole.
The blade assembly (43) is detachably attached to the head (40) and has a bottom, a top, a mounting base (44), a fastener and a blade (46). The mounting base (44) is formed on the bottom of the blade assembly (43) and is detachably mounted in the mounting recess (41) of the head (40) and has an inner side, a through hole and a guiding channel (45). The through hole is formed through the mounting base (44) and aligns with the threaded hole of the mounting recess (41). The guiding channel (45) is laterally formed through the inner side of the mounting base (44), communicates with the through hole of the mounting base (44) and is mounted around the holding protrusions (42) of the head (40). The fastener is mounted in the through hole of the mounting base (44), is screwed with the threaded hole of the mounting recess (41) to connect the blade assembly (43) with the head (40). The blade (46) is detachably mounted on the top of the blade assembly (43).
Although the blade (46) can be changed, a contacting area between the holding protrusion (42) of the head (40) and the guiding channel (45) of the blade assembly (43) is small, so the conventional boring bit is not secured strongly enough to resist heaving loading so use of the conventional boring bit is limited.
To overcome the shortcomings, the present invention tends to provide a boring bit to mitigate or obviate the aforementioned problems.